Means for measuring time of propagation of wave fronts over circuits



Feb. 9, 1932.

J. HERMAN MEANS FOR MEASURING TIME 0F PROPAGAITION OF' WAVE FRONTS OVER CIRCUITS Filed Dec. 2. 1927 INVENToR Jenma//z/ ATTORNEY Patented Feb. 9, 1932 l UNITED STATES* PATENT oFFicE JOSEPH HERNAN, F WESTFIELD, NEW JERSEY, yASSIG'NOR T0 AMERICAN TELEPHONE AN'D TELEGRAPH COMPANY, A CORPORATION 0F NEW YORK i FOR mSURING TIME 0F IPROPAGATION 0F WAVE Ji'RQNTS OVER CIRCUITS Application nieu December 2,1927. semi no. 237,300.

This invention relates to means for measurmg the time of propagation of a wave front over a circuit with currents of various frequencies.

instance wherein measurements of this character might be of value would bein the construction and design of new circuits, and v more particularly with respect to the design of networks to be utilized in such circuits to exualize the time of propagation thereover o currents of different frequencies. Other uses and features of the invention will appear more fully from the detailed description .hereinafter given.

The invention utilizes the measuring device disclosed in a copending application in the name of J. Herman, filed September 2, 1926, Serial No. 136,887 and which issued June 24 1931, as Patent No. 1,765,585. In 20 this device, the method of operation consists in charging a condenser during the interval of time to be measured, discharging this condenser through an indicating means, such as a( differential meter, adjusting the electrical 25 .constants of the charging circuit of the condenser by means of a variable resistance, re-

peating the above operations until the charge accumulated on the condenser is equal to a known charge, and utilizing the valuesof the electrical constants of the charging circuit when the charge accumulated on the condenser is equal to a known charge to determine the interval of timeto be measured. In the arrangements and method of the present invention, current of the frequency to be measured will be applied to, or cut offrom, one end of a circuit utilized as a.v standard for calibration purposes as soon as tlie condenser in the measuring set starts charging. This current will operate a relay at the other end of the circuit. This relay will control means for discharging the condenser of the measuring set. The interval of time between appli-v cation of the current and operation of the relay will represent the time of propa ation of the wave front over the circuit. This interval of time will be the measurement given by the set. The current of frequencyv invention.

The arrangements sliown in the drawing consist primarily of the circuit 1 whose delay is to be measured, an oscillator 2 for furnishing currents of different frequencies,lan amplifier-detector and a time measuring set 3. The `delay circuit 1 is terminated by resistances R8 and R, whose olimic values are equal to the characteristic impedance of the delay circuit. The input and output terminals of this circuit are connected, respectively, to the calibrate and measure po' sitions of a double-pole-double-tlirow switch SW whose mid-terminals are connected to the input of the amplier-detecton The output of oscillator 2 is connected through a resistance network N and a selective circuit 5 to the input of the delay circuit 1. At N the output circuit of the oscillator is bridged by the circuit 4 connected to one set of the contacts of the-starting relay Di in the measuring set 3. By connecting the circuit 4 to the network N as shown, the network N prevents undue change of the input impedance of the filter 5 when the short-circuit 4 is closed. A

change in the input impedance of the filter 5 the'detector tube are connected the milliammeter M'2 and the winding of relay D8. The latter is arranged to operate to .its m contact whenever current from the oscillator 2 is applied `to the input of the amplifier-detector. The time measuring set 3 comprises two relays D1 and D2,.the key K1, a diierentialmeter arrangement comprising'the .meter` M1 and the resistances R5 and R6, two condensers I l@ C1 and C2 and several batteries and resistances. lts operationwill be pointed out in more detail' later on.

' Before .a measurement can be made, the Y following adjustments are necessary; the selectivo circuit 5, ii used, should first be adjusted to the desired frequency, after which the oscillator should be adjusted to this same frequency and to the desired output current. l `With the key K open and switch SW on calibrate, the potentiometer P of the ampliier-detector is adjusted to give a direct current reading on meter M2 about twice that required to just operate relay D8. .This reading should be noted, since it will have to be duplicated when switch SW is on the measosition.

en these adjustments have been made, a calibration reading should be obtained. This calibration reading is the sum of the delay in the measuring set 3, the amplifierdetector and the selective circuit 5. lit is obtained by repeatedly operating the key K and adjusting the resistance R1 until meter M1 shows no deflection. 'lhe value of resistance 35 R1 is then a direct measure oi this delay, and

.45 the meter M1. lhe time corresponding to this set-up', as read from the scale oi R1, consist'sl of the calibration reading obtained above plug the delayin circuit 1. By subtracting the two values, the delay in circuit 1 is obtained for'y the particular frequency to which the oscillator was adjusted. For the delay at other frequencies, the above procedure must be'repeated. 1' ln order to more fully understand thel process by which the time measurement of the delay is made, a detailed description oi the operation oi the various circuit elements .will now be given. When thelrey K is open, as shown in the drawing, current'from the @il oscillator 2 Hows through the selective circuit 5 anda small part oi the current at the input of: circuit 1 ows through the high impedance potentiometer P, is amplied at V1 and detected at V2, thereby causing the armature I of relay'Dgto rest on its m contact and shortcircuit of condenser C1 through the resistcircuit the winding of relay D2. When lr'ey K is closed, relay D1 is operated, causing the output of oscillator 2 to be short-circuited and at the same time closing the charging p0 l ance R1 and battery B3. This condenser continues to charge until the detector relay D3 operates, allowing D2 to operate and open the charging circuit. The partially charged condenser C1 and the fully charged condenser 75 C2 are then connected diiierentially to meter M1. If the two charges are equal, no deiection of the meterwill occur. If they are unequal, dedection will be observed. gy repeatedly opening and closing'the key and readjusting the resistance R1, the Ytwo charges can be made equal and the elapsed time between the operation of D1 and of D2 is then indicated by thevalue of R1. rlhis elapsed time, as previously mentioned, consists of the zero error-of the measuring arrangement. When the measurment is made to the output instead of to the input of thedelay circuit l, the elapsed time consists oi the zero error plus the delay oi circuit l. By subtracting the results oi the two measurements, the value oi the delayin circuit l. is

readily obtained.

While the invention has been disclosed as embodied in certain specific arrangements which are deemed desirable, it is understood that it is-capable of embodiment in many'and other widely varied forms without departing from the spirit of theinvention as defined by the appended claims. 39@

What is claimed is:

1. rhe combination lof a time measuring set whereby a direct indication may be given of the time interval between the'control of a current source associated with one end of a circuit and the o eration of responsive means at the other en of said circuit, with a line having a delay circuit therein to be measured, means to apply a source of alternating current waves to one end ci said line, a responsive means adapted to be connected to the other end of said line, switching means whereby said line may be completed with or without the inclusion therein of said delay circuit, means for starting the operation of said measuring set, means for simultaneously controlling the transmission of current trom A said source to said line, means controlled by said responsive means for completing the operation of said measuring set, and means inserted in said line between said responsive means and said means iorcontrolling transmission vto prevent the transmission of transients due to the operation of said transmission controlling means.

' .2. The combination of a time measuring set whereby a direct indication may beY 'ven of the time interval between the contro of a current source associated withV one end oi a circuit andthe operationo responsive '13@ f means at the other end of said circuit, with a line having a delay circuit therein to be 'measured, means to apply a source of alterhating current waves to one end of said line, a responsive means adapted to be connected to the other end of said line, switching means whereby said line may be completed with or Without the inclusion therein of said delay circuit, means for starting the operation of said measuring set, means for simultaneously controlling the transmission of current from said source to said line, means controlled by said responsive means for completing the operation of said measuring set, a filter inserted in said line between said responsive means and said means for controlling transmission, said filter suppressing transients due to the operation of said transmission controlling means, and means associated with the input side of said filter to prevent substantial change in the input impedance of the filter when said transmission controlling means is operated.

In testimony whereof, I have signed my` name to this specification this 1st day of December, 1927.

. JOSEPH HERMAN. 

